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I have been crusing through this site and noticed there is a lot of misinformation and confusion about oil. Here are a few things you should know about oil for BMW's:

1) All new BMW's require synthetic. As far as weight, only certain production dates of M3's and M5's require the use of Castrol TWS 10w-60.

2) The Factory BMW Synth 5w-30 is a version of Castrol TXT Softect sold overseas. A few important things about the BMW oil a) it is a Group III hydrocracked oil which cannot be called synthetic in Europe, b) it is a heavy 30 weight (30 weight can run from 9.3-12.5cst@100c, the BMW oil is about 12.2cst), c) it is a ACEA A3 oil which means that it is approved for longer change intervals and has a HTHS (High Tempurature High Shear) measured at 150c of greater than 3.5.

3) In the US, the only Group IV PAO Synthetics that are available are 1) Mobil 1, 2) Amsoil (but not the Xl-7500), 3) Royal Purple, and 4) German Castrol 0w-30 (it has the red label and says on the back, "Made in Germany). Redline is a Group V PolyEster based oil. All other Castrol, Quaker State, Pennzoil, Valvoline "synthetics" are a Group III hydrocracked oil. It is debated how much better Group IV base oils are than group III, but generally they are considered better.

4) When looking for oil for any BMW that does not require Castrol TWS 10w-60, you want to purchase an oil that has either/both of the following ratings, a) ACEA A3, or b) BMW LL-98 or LL-01.

5) Note that Mobil 1 0w-30, 5w-30, and 10w-30 are NOT ACEA A3 or BMW LL approved oils. This is because they all are thin 30 weight oils (approximately 9.8-10 CST@ 100c) and have HTHS of approximately 3.1. Mobil 1 0w-40 and 15w-50 are A3 rated and the Ow-40 is BMW LL-01 approved. For 99% of climates and users 0w-40 or 5w-40 is the appropriate grade. There are some 0w-30 and 5w-30 oils (like the BMW 5w-30) that are forumlated on the heavier end of the 30 weight scale and are accordingly rated A3. These oils will work well also. LOOK FOR THAT ACEA A3 rating. If the oil doesn't have it, pass on it.

6) Some people seem confused about how oil thickness is measured. The first number (0W, 5w, 10w, 15w, etc) is a measurement of how thick the oil is at tempuratures of -35c- -20c (depends on the grade). The lower this first number the thinner the oil is at LOW tempuratures. The second number (30, 40, 50) refers to oil thickness at 100c (operating tempurature). 30 weight can be from 9.3-12.5 cst, 40 weight from 12.6-16.2 cst, 50 weight from 16.3-22cst (approximate). So you can have two oils, one called a 5w-30 (i.e. bmw oil) another 0w-40 (Mobil 1) that are very similar thicknesses at operating tempurature. Compare this to Mobil 1 Xw-30 which is close to a 20 weight oil at 100c. For more information here is a link with exact numbers http://www.bobistheoilguy.com/visc.html

7) BMW's recommended interval of 12,000-15,000 miles is to long. Used oil analysis has shown the BMW oil is generally depleted at 10,000 miles. Running it longer results in excess wear. It is highly recommended that you change your oil once between each BMW recommended interval (approx 7000-7500 miles). If you want to run your oil the BMW recommended interval, I would suggest that you use Mobil 1 0w-40 or Amsoil 5w-40 and change the oil filter at 7500 miles. I would encourage a full oil change at 7500 if you want your engine to last.

8) If you want to spend a few hours learning about oil, go to bobistheoilguy.com

great post i used to run mobil 1 0w-40, but recently changed to redline 5w-30. does redline being group 5 mean it's "better"? are you recommending mobil 1 0w-40 over redline?

Group V does not necessarly mean better. Redline tends to run heavy for its grade so 5w-30 is a fine grade. Note that Redline is NOT API rated so potentially if you have an oil related failure BMW could deny your warrantee. Personally, I think that Redline is a great oil and if you like it would stick with it. I continue to use the Mobil 1 because 1) it is more widely available, and 2) it is cheaper at $4.75 quart v. Redline at $6.25 quart locally.

1) The TWS 10w-60 is a very specific oil and likely a Group IV/V blend. The reason that BMW specifically recommends and imports it is there is no equivilant oil in the US. In Europe, Shell & a few others make an equivilant 10w-60.

2) For Autocrossing and Lapping on Hot Days. For autocrossing, the 0w-40 is fine as you do not see high sustained oil temps. For lapping days, you may want to consider 15w-50 as you will high sustained oil temps.

3) The BMW 5w-30 Synthetic. This is a good oil at a fair price ($4.00). Mobil 1 0w-40 is a better oil, especially for longer change intervals. The problem is the combo of the BMW oil and 15,000 mile oil changes is not a good one.

4) A note concerning Mobil 1 5w-40 SUV oil. I know that somebody is going to go to buy this and say "hey it doesn't say ACEA A3 on the back." They are correct. The 5w-40 oil repackaged Mobil Delvac 1, a Synthetic Heavy Duty Engine oil originally designed for trucks and fleet vehicles. This oil is slightly heavier than the 0w-40 and has an HTHS of 4.1. It meets ACEA E3,4 & 5 which are diesal requirements but still require an HTHS of greater than 3.5.

What do you mean by that? All E39/E46 M3/M5 requires 10w-60. Perhaps you might want to change that to read "All E46/E39 M3/M5 require the use of Castrol TWS 10w-60."

I was looking at an old bulliten concerning the E46 M3 that had dates. It looks like from what I see that all E46 M3's spec 10w-60 and e39 M5's use 10w-60 for engines before 3/00 and 5w-30 for engines after that date. That information may be innacurate though.

Cary, so much info. You rock man.
I feel like I'm back in college, but it's all soaking in. . Are you a bio-chemist specializing in pertroleum or something? Thanks again man. You can never have enough information/facts about cars.....at least on this board.

A lil off topic, but whats a good tranny fluid to use, and change interval?

I personally like Redline Tranny Fluids for both manual and automatic transmissions. Which fluid you use depends on what your transmission originally required. If you e-mail redline they will tell you what they recommend. Generally a 30,000 mile change interval is what I find best.

IMPORTANT CAVEAT: BMW Automatic transmissions use so many different types of fluid it is hard to keep straight. Be very careful what you use and follow the manufacture guidlines. I know the ZF trannies use special shellor Texaco fluids that cannot be substituted with normal ATF fluids. Here is a link to a chart with the different fluid requirements.